1. Field of the Invention
An aspect of the present invention relates to a power supply apparatus, and more particularly, to a power supply input device for converting a discharge resistance in a power supply apparatus.
2. Description of the Related Art
Due to the depletion of fossil fuels and environmental problems, restrictions are being enforced to reduce a standby power of an electric or electronic device thus reducing unnecessary energy consumption. Therefore, a technique for reducing the standby power is being used as a marketing point that appeals to users.
FIG. 1 is a block diagram illustrating a conventional power supply input device having a discharge resistance. The conventional power supply input device includes an alternating current (AC) power supply unit 10, a line filter 20, a bridge diode 30, a direct current (DC) condenser 40, and a discharge resistance unit 50 that is connected to both terminals of the DC condenser 40 of the conventional power supply input device.
The discharge resistance unit 50 has the following functions. If an input supply voltage of a power supply apparatus that is being operated is momentarily applied, electrical energy stored in the DC condenser 40 is consumed only by its effective series resistance (ESR). Therefore, a potential of the DC condenser 40 gradually decreases.
However, according to the characteristics of a pulse width modulation (PWM) integrated circuit (IC) that controls the power supply apparatus, only when the DC potential decreases to a predetermined voltage or less, the power supply apparatus is reset and normally operated. Therefore, when a user applies the input supply voltage in order to re-operate the system before the DC potential decreases to the reset voltage or less, there is a problem in that the PWM IC is not reset and cannot be re-operated.
To solve the aforementioned problem, the discharge resistance unit 50 is provided to both terminals of the DC condenser 40 so that the DC condenser 40 can be rapidly discharged. However, when the discharge resistance unit 50 is used as described above, and the system is in a standby mode, a large amount of energy is lost by the discharge resistance unit 50 of the power supply apparatus. When the system has a high input voltage or uses a voltage doubler, the energy loss further increases, and a standby current efficiency of the system may further decrease.